The invention relates to a device for generating a trigger signal from the ignition pulses of an ignition system, preferably in an internal-combustion engine. German Patent 2,443,403 discloses an ignition system which includes an ignition coil and an interrupt switch disposed in the primary circuit of the ignition coil. In order to influence the running behavior of an internal-combustion engine operated with an ignition system, a controllable switch is provided which together with an actuation switch device can be connected in parallel with the primary winding of the ignition coil and thus suppresses individual ignition processes in the internal-combustion engine. The suppression of individual ignition processes is employed, for example, for a compression check in the internal-combustion engine with utilization of the starter current or for performance and smooth engine run measurements. To be able, to easily associate the current with the individual cylinders for a compression check, a connected engine tester requires reliable information about each individual ignition pulse occurring in the ignition system, independently of whether the ignition pulse initiates an ignition process or not.
It is generally known in the art to derive a trigger signal corresponding to the ignition pulses from the primary of the ignition coil. The signals that can be picked up there have numerous interferences superposed on them and exhibit varying signal behavior as a function of initiated or suppressed ignition processes.
It is the object of the invention to provide a device for generating a trigger signal from ignition pulses of an ignition system in which each one of the ignition pulses occurring in the ignition system is represented.